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Astro Slide - Hardware / Re: Astro camera, weird artifacts when looking more closely
« on: February 09, 2023, 07:25:25 pm »
I'm out and about at the moment, but will try too post again with examples later. The Astro uses a quad bayer sensor. This means instead of the normal bayer pattern, you have 4 pixels in a square for each colour. You normally have one line with green, red, green red etc, and another with blue, green, blue, green etc. The cmera device interpolates (guesses) what the colour shouuld be where it is missing. Green is most sensitive to the human eye, hence it has twice the pixels. In a quad bayer, it has to do more guessing on the colour. Secndly, quad bayer tends to be used with high pixel sensors, so each well (pixel) is quite small.
Appoologies in advance fr the physics stuff......
A pixel is like a bucket, and photons (light) are ike rain dops. The drops fall into the buckets, and if you time the exposure to the rain, the bucket will fill up dependiing on how much rain goes in. A small bucket still fills up to the same height as a large bucket in heavy rain, however in light rain, if the bucket is small, it starts missing rain drops. Sometimes it might get a few eetra, some times a few less. This is noise. The larger the bucket, the lower the percentage of missed or extra raindrops and the more accurate the reading of how much rain was captured.
So going back to cameras, the bucket is a pixel on a sensor, and the image is made up of the levels of all the bckets. The larger the bucket, the lower the noise. When more photons bombard the well, the lower the noise. Combinnig pixels in a quad bayer sensor results in effectively a bigger bucket. Interpolating (guessing) also adds noise, so using the full sensor wll result in more noise than pixel binning (bigger bucket). Add in to this HDR, which amplifies llow light levels and you add even more noise. I did a few very quick tests, and using the default camera (not open camera), when you select 12MP and turn off HDR, you actually get quite an impreessively low noise, high quality image.
What I am trying to say in this overly long, but hopefully helpful post, is that the noise is a result of the processing options chosen for the photo. High res, hdr images will produce large gobs of noise when you zoom in, but lok quite good zoomeed out. For the best result, give the camera a chance and shoot 12MP, low ISO (if available) and turn off HDR.
Phones like the pixels, iphones, galaxies have even mre tricks and take multiple photos, averaging them to remove noise. That is called computational photography. You can do this yourself after the fact on a PC with excellent results if you really want.
I'll post examples later today.
Appoologies in advance fr the physics stuff......
A pixel is like a bucket, and photons (light) are ike rain dops. The drops fall into the buckets, and if you time the exposure to the rain, the bucket will fill up dependiing on how much rain goes in. A small bucket still fills up to the same height as a large bucket in heavy rain, however in light rain, if the bucket is small, it starts missing rain drops. Sometimes it might get a few eetra, some times a few less. This is noise. The larger the bucket, the lower the percentage of missed or extra raindrops and the more accurate the reading of how much rain was captured.
So going back to cameras, the bucket is a pixel on a sensor, and the image is made up of the levels of all the bckets. The larger the bucket, the lower the noise. When more photons bombard the well, the lower the noise. Combinnig pixels in a quad bayer sensor results in effectively a bigger bucket. Interpolating (guessing) also adds noise, so using the full sensor wll result in more noise than pixel binning (bigger bucket). Add in to this HDR, which amplifies llow light levels and you add even more noise. I did a few very quick tests, and using the default camera (not open camera), when you select 12MP and turn off HDR, you actually get quite an impreessively low noise, high quality image.
What I am trying to say in this overly long, but hopefully helpful post, is that the noise is a result of the processing options chosen for the photo. High res, hdr images will produce large gobs of noise when you zoom in, but lok quite good zoomeed out. For the best result, give the camera a chance and shoot 12MP, low ISO (if available) and turn off HDR.
Phones like the pixels, iphones, galaxies have even mre tricks and take multiple photos, averaging them to remove noise. That is called computational photography. You can do this yourself after the fact on a PC with excellent results if you really want.
I'll post examples later today.
